1. Field of the Invention
The present invention relates to a two-way clutch used in a power transmission mechanism, an auxiliary machinery or accessory driving system, or the like, of a car.
2. Related Background Art
A two-way clutch is used as means for switching power transmission paths in a power transmission mechanism, a driving system for an accessory, or the like, of a car. For example, in a hybrid car having two power sources including an internal combustion engine and an electric motor, when the car is driven by the electric motor, in addition to the internal combustion engine, a rotation of the electric motor is transmitted to an output shaft through a two-way clutch in both directions of forward and backward rotations. A two-way clutch is employed also in an accessory driving system additionally using an electric motor, a center differential gear of a four-wheeled vehicle, or the like. (See, for example, Japanese Patent Application Laid-Open No. 2002-5200 (page 3, FIG. 3), Japanese Patent Application Laid-Open No. 6-344796 (page 3, FIG. 2), Japanese Patent Application Laid-Open No. 10-53044 (page 4, FIG. 2), Japanese Patent Application Laid-Open No. 7-42767 (page 2, FIG. 2), Japanese Patent Application Laid-Open No. 9-25959 (page 4, FIG. 1) and U.S. Pat. No. 3,295,625 (page 1, FIG. 2))
The two-way clutch described above employs such a structure that a cylindrical surface is formed on either one of an inner race element and an outer race element, the cam surfaces are formed on the other of the inner race element and the outer race element, and the torque transmission members such as rollers or sprags are interposed between the cylindrical surface and the respective cam surfaces, so that each torque transmission member is retained at the neutral position or one of engagement positions of the cam surface and the phases of a cage for retaining the torque transmission members are changed by the use of an electromagnetic clutch mechanism or a frictional drive mechanism. However, in such a clutch in which the torque transmission members are retained at the respective neutral positions of the cam surfaces, each torque transmission member is retained by two biasing means inside the cage, so that the number of constituent parts and the manufacturing cost are increased. On the other hand, in such a clutch in which the torque transmission members are retained respectively at the engagement positions of the corresponding cam surfaces, the cylindrical surface and the torque transmission members are brought into sliding contact with each other so that fuel expenses or the like may be increased due to a dragging torque when the two-way clutch is not operated.
The present invention has be contrived taking the above circumstances into consideration, and an object thereof is to provide a two-way clutch with a less power loss in a comparatively simple structure.
In order to solve the above problems, according to the present invention, there is provided a two-way clutch comprising: an inner race element provided with one of a cam surface and a cylindrical surface; an outer race element provided with the other of the cam surface and the cylindrical surface; a torque transmission member interposed between the cam surface and the cylindrical surface for performing torque transmission between the inner race element and the outer race element; biasing means for biasing the torque transmission member in a direction substantially along the cam surface; and a cage for retaining the torque transmission member and the biasing means, the cage being supported to be rotatable relative with the cam surface, wherein the cage is elastically retained by elastic retaining means at a position where the torque transmission member is in a neutral condition with respect to the cam surface, and the biasing means is provided only on one side of the torque transmission member.
According to an aspect of the present invention, the two-way clutch may further comprise an extension portion formed on the cage to be extended in the axial direction with respect to either the inner race element or the outer race element whichever serves as a cam surface side element having the cam surface; and frictional drive means interposed between the extension portion and the cam surface side element for frictionally transmitting a rotary force of the cam surface side element to the cage to thereby rotate the cage relatively with the cam surface side element.
The two-way clutch of the aspect of the present invention, the frictional drive means may comprise: a differential element or a stationary element which is retained to be rotatable relatively with the extension portion; a frictional surface which is formed integrally with or separately from the extension portion to be slidably contacted with the differential element or the stationary element; another frictional surface which is formed integrally with or separately from the differential element or the stationary element to be slidably contacted with the extension portion; and pressing means for bringing a frictional surface on the side of the differential element or the stationary element into pressure contact with a frictional surface on the side of the extension portion.
In the two-way clutch of the present invention, the inner race element may be provided with a lubricating oil path for supplying a lubricating oil to a contact portion between the inner race element and the torque transmission member.
In the two-way clutch of the present invention, the cage may be provided with a lubricating oil path for supplying a lubricating oil to the frictional surface of the frictional drive means.
In the two-way clutch of the present invention, the torque transmission member may be a roller.